The present invention relates to a laser scanner system, which has a plurality of scanners and acquires point cloud data in a wide range.
As one of the usage methods of a laser scanner, a method is known, in which laser scanners are installed on a movable object such as an automobile and acquire point cloud data of a predetermined range along a moving line. A point cloud data thus acquired is used as a map data of a navigation system or is used for measuring a shape of building structure or is used as a data for judging a condition of a road surface.
As one of the laser scanners, there is a laser scanner of TOF (TIME OF FLIGHT) type. The laser scanner emits a laser beam (a distance measuring light) by pulsed emitting, measures a distance of a projecting point (a measuring point) per each pulsed light by receiving a reflected light and based on a time required for a round trip of the pulsed light, and further, by scanning the laser beam within a range as required, point cloud data are acquired.
Conventionally, in a case where a laser scanner is installed on a movable object, e.g. an automobile, the laser scanner is installed at a part where a visual field from the automobile is opened, e.g. one laser scanner is installed on a ceiling of the automobile, the emitted laser beam is scanned in a direction crossing a moving line, and the point cloud data within a predetermined range along the moving line is acquired.
In a case where the point cloud data are acquired by the laser scanner installed on the automobile, it is desirable that the automobile runs at the same speed as other vehicles. Further, in order to improve the measurement accuracy, it is desirable that the point cloud data are becoming denser. On the other hand, the density of the acquired point cloud data is determined by a scanning speed of the laser beam, a moving speed of the automobile and a light emission frequency of the pulsed light.
Therefore, in order that a predetermined point cloud data density is satisfied under the condition where high density of the point cloud data is required, an increase of the light emission frequency is required. However, because of a restriction on a duty of a light emitting source, the increase of the light emission frequency is limited, and there have been problems where demands of a higher moving speed and a higher density of the point cloud data may have not been fulfilled sufficiently.